Sun
rays, also called crepuscular rays, streaming through gaps in clouds
are parallel columns of sunlit air separated by darker cloud shadowed
regions. The rays appear to diverge because of perspective effects,
like the parallel furrows of freshly ploughed fields or a road wide
at your feet yet apparently narrowing with distance. Airborne dust,
inorganic salts, organic aerosols, small water droplets and the air
molecules themselves scatter the sunlight and make the rays visible.